The invention relates to an apparatus for changing objective lenses in a microscope. In particular, the invention relates to an objective lens changing device for a microscope that is used in conjunction with a stage and a fixed stage.
When investigating sections of living tissue, it is usual to use an upright- microscope, since observation and measurement must occur from above. A plurality of manipulators, having needles or capillaries, are located in the region of the object and thus close to the objective lens. It is usual to use for this purpose a microscope having a fixed stage, in which the objective lenses are then moved for focusing. This is necessary because the manipulators do not allow movement of the stage. These microscopes are characterized in general by their crowded configuration. For example, one objective lens and at least one manipulator are directed toward one object point. These applications also require special objective lenses that are of slender configuration at the tip so that the needles can approach a sample at a certain angle. The needles or manipulators must approach samples at a certain angle to allow proper action on the preparations. Because of the substantially lateral pivoting motion, the objective lens turrets used in conventional microscopes would result in a collision between the objective lenses and manipulators. The objects being observed with the microscope are in many cases sections, cells, or cell cultures that are usually immersed in a physiological liquid. This liquid is in turn covered over. The cover is equipped with an opening through which the objective lenses can be immersed into the liquid. In order to change the objective lens, it is therefore necessary first to pull it out vertically before any pivoting motion is possible. This vertical motion is generally performed using the focusing device. Low-magnification objective lenses usually also have a greater working distance, The layer of a physiological liquid can be very thin (e.g. so that the stronger objective lenses cannot be immersed too deeply). The low-magnification objective lenses must therefore be lowered beyond the local point (and then lifted again) to create an appropriate contact with the liquid. ZEISS and NIKON offer objective lens changing devices which eliminate the pivoting motion of the objective lenses. Changing is accomplished via a combination of linear notions. In other words, first a vertical motion is performed and then an offset forward or backward, so as to displace other objective lenses located on the objective lens turret into the beam path. The mechanism necessary for this purpose is, however, not particularly stable, and in addition requires an undesirably large actuation force. Moreover, it allows changing only between two objective lenses, and also cannot readily be motorized. The brief lowering of the objective lenses that may be necessary (in order to make contact with the liquid) must still be effected separately using the focusing device. The automated microscopes of the LEICA company currently on the market, with the model designations DMRA RXA, and IRBE, lift the objective lenses away from the preparation (for immersion objective lenses) before the objective lens turret rotates and thus displaces another objective lens into the beam path.
It is an object of the present invention to create an objective lens changing device with which objective lenses can be changed in simple, motor-driven, reliable, and economical fashion. It is also an object of the present invention to provide an apparatus for objective lens changing that is suitable for performing a requisite vertical motion during the objective lens change in order to change the immersion objective lenses. The present invention also allows one to return quickly and reliably to a point on the preparation after the objective lens change. These objects are achieved by an apparatus for changing an objective lens in a microscope with a fixed stage, The microscope further comprises one end wall and two side walls joined by the end wall, and an objective lens turret which defines a rotational axis that is arranged obliquely with respect to one side wall. These objects are firer achieved by a microscope comprising a stand in which one end wall and two side walls joined by the end wall are defined, and an objective lens turret which defines a rotational axis that is arranged obliquely with respect to one side wall. The objects are further achieved by a microscope having a microscope stand defining one end wall and two side walls joined by the end wall, and having an objective lens turret that brings multiple objective lenses into a working position. The objective lens turret is positioned to allow the objective lens to engage in substantially linear motion parallel to the stage place during the lens changing procedure.
The advantage of the present invention is that the rotary motion of a conventional objective lens turret is economical and precise. The rotary motion of an objective lens turret can be easily and reliably Motorized. If the rotational axis is located obliquely with respect to a side wall of the microscope stand, the pivoting motion of the objective lenses into or out of the working position thus occurs substantially as a motion identical to a back-and-forth motion. In other words, the motion of the objective lens in the region of the working position is substantially linear. This fact offers the particular advantage that such motion prevents any collision between the manipulators and the objective lenses mounted on the objective lens turret. It is self-evident that an obliquely arranged objective lens turret of this kind can also be fitted with more than two objective lenses without becoming cumbersome and without losing the above described advantages of the lens changing arrangement and of the objective lens turret. A further advantage of the invention results from a coordinated action of the motor drive of a fine-focus apparatus and the motor drive of the objective lens turret. The coordinated action of the two different motor drives makes it possible to achieve the preferred automation of the objective lens change and a simultaneous refocusing.